In 2017, an estimated 1.3 million individuals were living with a hematologic malignancy (HM: leukemia, myeloma or lymphoma) in the US. Frontline use of systemic high-intensity chemotherapy with or without radiation characterizes the management of HM. Patients with progressive disease or at high risk of relapse are treated with even higher intensity chemotherapy/radiation and blood or marrow transplantation (BMT); indeed, BMT is often the only curative option for these patients. Steady improvements in outcome have resulted in a growing number of BMT-HM survivors ? a population that is uniquely vulnerable to long-term chronic health conditions (CHCs) that are directly related to the high-intensity therapeutic exposures (e.g., subsequent neoplasms, heart failure). In 2000, we constructed a retrospective cohort of 2,333 BMT recipients (City of Hope [COH] or University of Minnesota [UMN]; BMT: 1974-1998), who had survived ?2y (BMT Survivor Study [BMTSS]; R01 CA78938, Bhatia). While BMTSS has successfully described the high burden of morbidity, accelerated aging and premature mortality in BMT-HM patients, the modest sample size (n=2,333) and the older transplant era (1974-1998) has limited the potential for new discoveries, especially in the face of evolving treatment strategies. We propose a significant enhancement of the existing BMTSS cohort to now include 10,042 HM patients treated with BMT between 1974 and 2014 at COH, UMN or UAB (BMT-HM), as well as a frequency-matched cohort of 3000 HM patients treated with conventional therapy without BMT (non-BMT-HM). This enhanced infrastructure (BMTSS- 2) will be poised to determine the burden of morbidity borne by HM patients treated with or without BMT within the context of individual HM diagnoses, and to understand the pathogenesis of treatment-related health conditions in the setting of accelerated aging. The enhanced BMTSS-2 infrastructure will enable us to: i) understand the long-term risk of health conditions experienced by HM patients treated with and without BMT; ii) determine the association between treatment exposures and health conditions; iii) determine trends in health conditions with changes in treatment strategies; iv) identify interactions between preventable modifiers (comorbidities, health behaviors) and treatment exposures when determining risk of health conditions; v) study the pathogenesis of treatment-related health conditions in the setting of accelerated aging, using genetic markers for susceptibility and epigenetic markers for the association of the health conditions with aging; vi) use HIPAA- compliant technology platform compatible with iOS/Android/iPad/Web-based applications to educate HM patients and measure health behaviors in real time. This is the largest and most comprehensive attempt at examining the health and wellbeing of HM patients treated with and without BMT. The overarching goal is to use BMTSS-2 for translational research along two tracks: A) develop risk prediction models to identify HM recipients at highest risk of treatment-related health conditions; and B) among those identified to be at highest risk, design and test targeted interventions to prevent/ ameliorate these debilitating chronic health conditions.